1. Field of the Invention
The present invention relates to a head suspension for a disk drive incorporated in an information processing unit such as a personal computer and a method of manufacturing the suspension.
2. Description of the Related Art
A hard disk drive (HDD) used for an information processing unit has magnetic or magneto-optical disks to write and read data and a carriage. The carriage is turned around a spindle by a positioning motor.
The carriage is disclosed in, for example, U.S. Pat. No. 4,167,765. This carriage has arms, a head suspension (hereinafter referred to also as xe2x80x9csuspensionxe2x80x9d) attached to each arm, and a head attached to the suspension. The head has a slider. When each disk of the HDD is rotated at high speed, the slider slightly floats above the disk and air bearings are formed between the disk and the slider.
The suspension consists of a load beam, a flexure, and a base plate. The load beam is made of a thin precision resilient plate. The flexure is made of a very thin plate spring fixed to a front end of the load beam by, for example, laser welding. The base plate is fixed to a base of the load beam by, for example, laser welding and is fixed to each arm of the carriage.
Disks of recent HDDs are designed to densely record data and revolve at high speed. It is required, therefore, to provide a head suspension of improved vibration characteristics to carry out precision positioning of a head on a disk surface, as well as resistance to turbulence caused by the disks revolving at high speed. In addition, the suspension must be ready for intricate processes to provide new functions.
To deal with a high-density disk, the suspension must have high rigidity and a low spring constant. FIG. 1 shows a head suspension 101 for a disk drive according to a prior art. The suspension 101 has a load beam 103 that is solidly composed of a rigid part 103a of L1 in length and a resilient part 103b of L2 in length. It is hardly possible for this suspension 101 to simultaneously realize high rigidity for the rigid part 103a and a low spring constant for the resilient part 103b because the rigid part 103a and resilient part 103b are integrated with each other.
The material and thickness of the rigid part 103a are restricted by the resilient part 103b, and therefore, the rigid part 103a must improve the rigidity thereof by bends 105 or embossed ribs 107 that need additional precision processes to increase costs.
The bends 105 and ribs 107 disturb air flows and are easily influenced by turbulence due to disks rotating at high speed, to flutter the load beam 103.
The load beam 103 is fixed to a base plate 109, which is attached to a carriage arm of an HDD. To stably support the load beam 103 with the base plate 109, the base of the load beam 103 must not be thinner than a specified thickness. This restriction prevents the lowering of the spring constant of the resilient part 103b. 
A flexure 111 is fixed to the load beam 103. The flexure 111 has a head 113 including a slider 115.
A technique of lowering the spring constant of a load beam is disclosed in Japanese Unexamined Patent Publication No. 9-191004. This technique partly thins a resilient part of a load beam by partial etching. The partial etching, however, has a limit in precisely controlling the thickness of the resilient part, and therefore, causes variations in the thickness and spring constant of the resilient part.
Japanese Unexamined Patent Publication No. 8-128919 discloses a technique of forming narrow plate springs around a slider supporting part of a load beam by etching or press. This technique deforms the narrow plate springs in a thickness direction, which needs fine processes because the narrow plate springs must be formed in a small area, to deform the shape of the load beam, vary the spring constant thereof, and deteriorate quality.
An object of the present invention is to provide a head suspension of high performance to meet various requirements and method of manufacturing such a head suspension.
In order to accomplish the object, a first aspect of the present invention provides a head suspension for a disk drive, having a base plate to be attached to a carriage of the disk drive, and a load beam consisting of a rigid part and a resilient part, to apply load onto a slider. The rigid part and resilient part are separately formed, and the rigid part is joined to a first side of the resilient part. The suspension also has a reinforcing plate to hold and fix a second side of the resilient part between the reinforcing plate and the base plate.
The first aspect resiliently supports the load beam with the base plate through the resilient part. The material and thickness of the rigid part are not restricted by the resilient part because the first aspect separately forms the rigid part and resilient part with proper materials and thicknesses that meet their respective requirements to provide required performance for the suspension. For example, the rigid part is made of a thick plate to increase rigidity without bends or ribs and reduce air resistance. This results in reducing turbulence caused by the high-speed rotation of disks and preventing the fluttering of the suspension.
The first aspect stably holds the resilient part between the base plate and the reinforcing plate, so that the base plate may stably and resiliently support the rigid part through the resilient part. This three-layer structure of the base plate, resilient part, and reinforcing plate enables the resilient part to be thinned to secure a low spring constant. The low spring constant is also securable because the resilient part is formed independently of the rigid part. The first aspect simultaneously realizes stability, accuracy, and low spring constant for the resilient part.
The first aspect may form the rigid part from softer material than the resilient part. This expands the degree of freedom of the designing and processing of the rigid part.
A second aspect of the present invention provides the base plate with a boss protruding from the base plate in a thickness direction. The boss is fitted to a hole formed in the carriage, to fix the base plate to the carriage. The second aspect also provides each of the resilient part and reinforcing plate with a hole to receive the boss with at least one of the holes serving as a positioning hole that precisely fits the boss.
The second aspect correctly positions the load beam with respect to the base plate and sandwiches the resilient part between the base plate and the reinforcing plate. This results in stabilizing the manufacturing of the suspension.
A third aspect of the present invention makes each of the base plate and reinforcing plate thicker than the resilient part.
The third aspect firmly holds the resilient part between the base plate and the reinforcing plate and realizes a low spring constant.
A fourth aspect of the present invention provides a method of manufacturing a head suspension for a disk drive. The suspension has a base plate to be attached to a carriage of the disk drive, a load beam consisting of a rigid part and a resilient part, to apply load onto a slider, the rigid part and resilient part being separately formed, the rigid part being joined to a first side of the resilient part, and a reinforcing plate to hold and fix a second side of the resilient part between the reinforcing plate and the base plate. The method includes a first step of forming small holes in at least one of the base plate and reinforcing plate, and a second step of welding the base plate, resilient part, and reinforcing plate by emitting laser beams into the small holes, to fix the second side of the resilient part between the base plate and the reinforcing plate.
The fourth aspect welds the three-layer structure of the base plate, resilient part, and reinforcing plate together by emitting laser beams into the small holes. The use of the small holes saves laser power and surely welds the three layers together. Due to the low laser power, the fourth aspect reduces the influence of heat on the suspension and maintains precise flatness on the three-layer structure.
A fifth aspect of the present invention provides the base plate with a boss protruding from the base plate in a thickness direction. The boss is fitted to a hole formed in the carriage, to fix the base plate to the carriage. The fifth aspect also provides each of the resilient part and reinforcing plate with a hole to receive the boss, at least one of the holes serving as a positioning hole that precisely fits the boss. The fifth aspect forms, in the first step of the fourth aspect, small holes in at least one of the base plate and reinforcing plate on each side of the boss receiving hole. The fifth aspect welds, in the second step of the fourth aspect, the base plate, resilient part, and reinforcing plate by emitting laser beams into the small holes, to fix the second side of the resilient part between the base plate and the reinforcing plate.
The fifth aspect uses one of the holes formed through the reinforcing plate and resilient part as a precision positioning hole for the boss and precisely positions the load beam with respect to the base plate. At the same time, the fifth aspect holds the resilient part between the base plate and the reinforcing plate and welds them together on each side of the boss. The fifth aspect correctly and stably fabricates the suspension.